Compressed air nailing machine

ABSTRACT

A compressed air nailing machine comprising a flanged ring nut which slides on the terminal part of the cylinder in order to connect the lower opening with either the atmosphere or the compressed air reservoir.

United States Patent COMPRESSED AIR NAILING MACHINE 2 Claims, 3 Drawing Figs.

91/420, 91/469 1111. c1 ..F15b 11/08, 5151, 13/042 [50] Field of Search 91/404, 405, 461, 415, 300, 416, 469, 420

[56] References Cited UNITED STATES PATENTS 1,348,280 8/1920 Howell 91/300 3,479,926 11/1969 Hillier 91/404 Primary Examiner-Paul E. Maslousky Attorney-B. Edward Shlesinger ABSTRACT: A compressed air nailing machine comprising a flanged ring nut which slides on the terminal part of the cylinder in order to connect the lower opening with either the atmosphere or the compressed air reservoir.

COMPRESSED AIR NAILING MACHINE This invention relates to a pneumatic nailing machine of the type in which the individual metallic nails are violently expelled and driven by percussion blows caused by a hammer moved by a piston sliding in a cylinder.

It is known that in conventional pneumatic nailing machines, the return of the piston after expulsion of the nail or pin is carried out by the action of compressed air which is accumulated during the working stroke of the piston in the collecting chamber between the cylinder and tool body. It is also known that all these systems, especially in the case of nailing machines of considerable power with large diameter cylinders, give rise to disadvantages due mainly to the growing counterpressure which the piston meets during its working stroke and the consequent reduction in efficiency of the percussion blow.

Other known systems, in addition to wasting a part of the energy, prove to be unwieldy, they considerably limit the piston excursion, they require particular precision of construction and have movable parts in contact which require constant lubrication and are subjected to extensive wear.

The object of this invention is to eliminate said disadvantages by providing an arrangement in which during the whole of the descending phase of the piston, the cylinder chamber lying beneath the piston remains connected to atmosphere, and in which the return stroke takes place by the action of compressed air furnished directly from the principal reservoir.

The essential characteristic of the nailing machine is thus attained, i.e. a free and rapid descent of the piston during the working phase and a rapid piston rise without excessive waste of air during the rise itself.

This object is attained by the pneumatic nailing machine of the above-said type, comprising a flanged ring nut which slides in a airtight manner on the terminal part of the cylinder in order to alternately close or open communication between the lower cylinder opening and either the atmosphere or the compressed air reservoir, said flange constituting a differential piston with the cooperation of its faces which slides in an airtight manner in the interspace between the cylinder and the tool body, the interspace being subdivided by the flange into two chambers, an upper chamber in communication with the internal upper terminal part of the cylinder by way of a duct, and a lower chamber in communication with the compressed air reservoir, the area of the flange subjected to the pressure in the upper chamber being greater than the area of the flange subjected to the pressure in the lower chamber. In this way the ring nut, functioning as a valve, automatically controlled by the differential efiect of the compressed air, permits the descending and accelerating phase of the piston to be carried out with maximum efficiency, giving the air thrust by the piston a free path to atmosphere, and allows the piston rise to take place under the direct action of compressed air from the reservoir on the lower face of the piston.

For greater clarity the invention will be described hereunder with particular reference to the embodiment illustrated by way of example in the accompanying drawing in which:

FIG. I is a perspective view of the nailing machine;

FIG. 2 is an axial section through the principal body, one half ofwhich (to the left) showing the position of the members in the rest phase, and the other half (to the right) showing the position of the members in the nail expulsion phase.

The nailing machine shown is of the portable type comprising a principal hollow body 1 with a hollow handle 2 provided with a connection 3 for the compressed air feed pipe. In the cavity of the body 1 is mounted a cylinder 4 with an internal jacket 5, in which a piston 6 slides which is rigid with a rod 7 functioning as a percussion hammer for the expulsion of one nail or pin at a time by way of the guide hole formed in the rest plate 8, said nails or pins coming from the storage holder 9. The upper opening of the cylinder 4 is closed or opened by the annular cap 10 rigidly moved by the differential valve 11 controlled in the known way by a trigger 12. The reference numeral 13 indicates the cover of the top of the body 1, while reference numeral 14 indicates the impact pad for the piston at the end of its working stroke, said pad 14 being shaped so as to leave the slits 15 which connect the lower chamber of the cylinder 4 to atmosphere, free.

According to the invention, a ring nut 16 with a flange l6 slides in an airtight manner on the lateral terminal surface of the cylinder 4. Said ring nut when in its upper position leaves the slits 15 open, while in its lower position, with its edge hitting on the pad ,14, it closes the air passage through the slits. The flange of said ring nut divides the interspace between the cylinder 4 and body 1 into two chambers 17, 18, of which the chamber 17 is connected to the duct 20 which emerges inside the cylinder 4 by way of a small gauged hole 19 situated in the upper part of the jacket 5, while the chamber 18 is connected to the upper chamber 22, which functions as a compressed air reservoir, by way of the duct 21. The duct 21 extends downwards until it communicates with the hole 21, by way of the passage hole 23 formed in the wall of the mobile ring nut 16, and connects the reservoir 22 to the inside of the cylinder 4 when the flange is in the lower limiting position (see FIG. 2, right). The reference numeral 24 indicates the seal ring which separates the reservoir 22 from the interspace 17, 18.

The nailing machine illustrated operates in the following manner:

Starting from the rest position shown in FIG. 2 to the left, when the trigger is pulled this causes in a known manner the raising of the valve 11 and hence of the cap 10 by which means the piston 6 is violently thrust downwards in order to expel and drive the metallic nail or pin. During its downward stroke the piston 6 meets no resistance because the air contained in the lower chamber of the cylinder has a free path to atmosphere by way of the slits 15. At the beginning of its downward stroke the piston 6 uncovers the hole 19 and the air contained in the chamber 17 attains in consequence the pressure level existing in the reservoir 22, which is also equal to the pressure existing in the chamber 18.

As the upper face of the flange 16' has a greater surface area than the lower face, the ring nut 16 is thrust downwards because of the differential pressure until it presses against the pad 14, so closing the passage between the slits and the lower chamber of the cylinder 4, and opening instead the passage for the compressed air which penetrates into the lower chamber of the cylinder 4 by way of the duct 21 and the holes 21 and 23, thus acting on the lower face of the piston 6 which now can carry out its return stroke after closure of the feed into the cylinder 4 by means of the cap 10 which simultaneously opens the discharge through the duct 25. Meanwhile the pressure in the chamber 17 is discharged by way of the duct 20 and the gauged hole 19, because of which the higher pressure in the chamber 18 causes the ring nut to rise, in this way arranging the nailing machine for the next cycle.

It should be noted that the hole 19 must be sized so as to ensure a slight lag in the operation of the ring nut during the rise and fall of pressure in the chamber 17, this lag being necessary in order that the ring nut carries out its strokes just after the strokes of the piston and not before, in order to ensure regularity of the phases of the working cycle.

We claim:

1. A compressed air nailing machine of the type comprising a body connected to a supply of compressed air, and which contains a cylinder in which a hammer-carrying piston slides for the expulsion and percussion of individual metallic pins or nails, comprising a flanged ring nut which slides in an airtight manner on said cylinder in order to alternately close or open communication between an opening in the lower cylinder and either atmosphere or the compressed air supply, the flange of said nut engaging and sliding on the inside wall of said body and constituting a differential piston which slides in an airtight manner in the interspace between the cylinder and said body, the interspace being subdivided by the flange into two chambers, an upper chamber in communication with the internal duct which connects the upper chamber of said interspace to the internal upper part of the cylinder has a gauged and calibrated port in order to slow down the flow of air in order to cause operation of the ring nut with the lag required by the cycle. 

1. A compressed air nailing machine of the type comprising a body connected to a supply of compressed air, and which contains a cylinder in which a hammer-carrying piston slides for the expulsion and percussion of individual metallic pins or nails, comprising a flanged ring nut which slides in an airtight manner on said cylinder in order to alternately close or open communication between an opening in the lower cylinder and either atmosphere or the compressed air supply, the flange of said nut engaging and sliding on the inside wall of said body and constituting a differential piston which slides in an airtight manner in the interspace between the cylinder and said body, the interspace being subdivided by the flange into two chambers, an upper chamber in communication with the internal upper part of the cylinder by way of a duct, and a lower chamber in communication with said compressed air supply, the area of the flange subjected to the pressure in the upper chamber being greater than the area of the flange subjected to the pressure in the lower chamber.
 2. A nailing machine as claimed in claim 1, in which the duct which connects the upper chamber of said interspace to the internal upper part of the cylinder has a gauged and calibrated port in order to slow down the flow of air in order to cause operation of the ring nut with the lag required by the cycle. 